This invention relates to the production of a heat-reflecting glass plate, and more particularly to a method of coating a glass plate surface with a titanium oxide film by spraying a solution of a thermally decomposable organic compound of titanium onto a heated glass surface.
Titanium oxide is a typical coating material for producing a heat-reflecting glass plate. A well known method for coating one side of a glass plate with a titanium oxide film is the spraying of a solution of a thermally decomposable organic compound of titanium onto the glass surface while the glass plate is sufficiently heated. The titanium compound in the sprayed solution undergoes thermal decomposition on the heated glass surface to form titanium oxide. An example of the titanium compounds conventionally used for this purpose is alkoxyacetylacetonato titanium which is obtained by reaction of titanium with a monoalcohol and acetylacetone.
In industrial practice, however, the titanium oxide coating film formed by the above described method is often unsatisfactory in the closeness or strength of adhesion to the glass surface and/or smoothness of the coating film surface. An important cause of such defects in the titanium oxide coating film is considered to be partial hydrolysis pf the titanium compound in the spraying solution because of susceptibility of the titanium compound to moisture present in the spraying atmosphere and even in the solution. Therefore, strict control of humidity becomes a requisite for the spray coating operation and also for the preparation and maintenance of the titanium compound solution. However, the exercise of such humidity control becomes a cause of lowering of the productivity, and this is a matter of serious concern particularly in the case of continuously producing heat-reflecting glass sheet by performing the spray coating operation before cooling of a glass sheet travelling along a continuous glass sheet production line.